1. Field of the Invention
The embodiments of the invention relate to a gamma voltage generation unit. Also, the embodiments of the invention relate to a display device.
2. Description of the Related Art
Flat display devices with features of slimness, lighter weight, lower power consumption and so on are being actively researched, developed or mass-produced. The flat display devices include liquid crystal display (LCD) devices, plasma display devices, field emission display devices, organic light-emitting display (OLED) devices or others.
Among the flat display devices, the LCD devices are being applied to mobile terminals, navigation devices, cameras, camcorders or others which have small sized screens. Also, the LCD devices are being applied to netbooks, notebook computers or others which have middle sized screens. Moreover, the LCD devices are being applied to television receivers, electric display board and so on which have large sized screens.
In particular, many special functions are added to the mobile terminal. As such, the mobile terminal becomes a necessity, for which modern society cannot do without. Actually, the mobile terminal can allow a user to retrieve, input, check and transmit information regardless of time, place, weather and so on. In other words, the mobile terminal is always being used by the user regardless of place, which includes the interior and the exterior, and time, which includes day and night.
However, visibility of the mobile terminal must be varied for the interior or the exterior, and for day or night, even though the information is displayed on the display device of the mobile terminal in the same brightness. In particular, visibility of the display device of the mobile terminal deteriorates in cloudy weather, a dark evening and so on.
To address this matter, a method of adjusting brightness on the basis of light intensity from a photo sensor is disclosed in Korean registered patent no. KR10-0418889 (hereinafter, ‘prior document 1’).
The prior art method disclosed in the prior document 1 increases the output value of a digital data signal in order to enhance visibility. In detail, a low data signal is modulated into a lower value than its value, and a high data signal is modulated into a higher value than its value. As such, the modulated low and high data signals cannot provide the attributions of original data signals. Furthermore, the data can be lost. Due to this, image distortion or/and non-desired faults can be caused.
Such a data modulation for enhancing visibility can be performed according to previously set three modes. Because the data modulation is limited to the three modes, it is difficult to increase brightness beyond a critical value. When the number of modes increases, the size of code used to set the increased modes must be enlarged.
Meanwhile, if an LCD device is used as a display device of the mobile terminal, visibility can be enhanced by adjusting brightness of a backlight unit. In this instance, black brightness for a black level can also increase. Due to this, a contrast ratio must become lower.